Validating transactions through Proof-of-Work (PoW) requires an incredible amount of processing power, which leads to high energy consumption. Bitcoin, the most prominent PoW blockchain, uses “at least 2.55 gigawatts of electricity currently, and potentially 7.67 gigawatts in the future." The carbon emissions required to produce this quantity of energy raise serious climate change concerns.

Energy usage of Proof-of-Work

University of Minnesota - Twin Cities

Transactions are grouped into blocks and the system works to make the block's hash contain a certain number of leading zero bits. Once a proof-of-work is completed, a block cannot be changed unless the work is redone. As more blocks are added to the chain, changing the block would require redoing the work for all the following blocks too. A result of this system is that the network accepts the longest chain as the legitimate chain.

Proof-of-Work

Saleh, Fahad. (2021). Blockchain Without Waste: Proof-of-Stake. Wake Forest University. https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3183935


Blockchain Without Waste: Proof-of-Stake

The Bitcoin Network functions in the following way:
Firstly, new transactions are broadcasted to all nodes. Then, each node gathers new transactions into a block. Next, each node works on finding a Proof-of-Work for its block. Once found, it broadcasts the block with the resultant PoW hash to all nodes. Nodes accept the block only if all transactions in it are valid and not already spent. Nodes express their acceptance of the block by working on creating the next block in the chain, using the hash of the accepted block as the previous hash.


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